1. Field
One embodiment of the invention relates to a sound quality correction apparatus, a sound quality correction method and a program for sound quality correction which each adaptively apply a sound quality correction process to a speech signal and a music signal included in an audio (audio frequency) signal to be reproduced.
2. Description of the Related Art
As is well known, for example, in broadcasting receiving devices to receive television broadcasting, information reproducing devices to reproduce recorded information from information recording media, and the like, when an audio signal is reproduced from a received broadcasting signal or a signal read from a information recording medium, a sound quality correction process is applied to the audio signal so as to achieve higher sound quality.
In this case, the content of the sound quality correction process applied to the audio signal differs depending on whether the audio signal is a speech signal, such as a voice, or a music (non-speech) signal, such as a composition. That is, regarding a speech signal, its sound duality is improved by applying a sound quality correction process to it to emphasize its center localization for clarification, as in talk scenes and sport live reports, whereas regarding a music signal, its sound quality is improved by applying a sound quality correction process to it to provide it with expansion with emphasized feeling of stereo.
Therefore, it is being considered to determine whether an acquired audio signal is a speech signal or a music signal and perform the corresponding sound quality correction process depending on the determination result. However, since a speech signal and a music signal are often mixed together in an actual audio signal, distinguishing between the speech signal and the music signal is difficult. Therefore, at present, a suitable sound quality correction process is not applied to an audio signal.
Disclosed in Jpn. Pat. Appln. KOKAI Publication No. 7-13586 is that an acoustic signal is classified into three kinds, “speech”, “non-speech” and “undetermined”, by analyzing the number of zero-crossing, power variations and the like of the input acoustic signal, and the frequency characteristics for the acoustic signal are controlled such that a characteristic of emphasizing a speech band is kept when the acoustic signal is determined to be “speech”, a flat characteristic is kept when the acoustic signal is determined to be “non-speech”, and a characteristic of the preceding determination is kept when the acoustic signal is determined to be “undetermined”.